Impact wrench



March 5, 1957 E. H. sHAFF 2,783,863

IMPACT WRENCH Filed Feb. 23. 19.54

2 shets-sheet 1 (Erneut/ O4 Uh@ March 5, 1957 E, H SHAFF 2,783,863

IMPACT WRENCH Filed Feb. 2 5, 1954 2 Sheets-Sheet 2 CT-romsy/ nited States Patent IMPACT WRENCH Ernest H. Shaft, Penn Park, Ind., assigner, by mesne assignments, to Gardner-Denver Company, a corporation of Delaware Application February 23, 1954, Serial No. 411,941 8 Claims. (Cl. 192-30.5)

The present invention relates generally to portable power operated tools for running and setting threaded fastening elements, and more particularly, to such tools of the impact type whereby a series of hammer-like blows are imparted to a fastening element either to finally set it after it has been run down tight or alternatively to initially loosen an already set fastening element.

It is a general object of the present invention to provide a wrench ofthe foregoing type which is characterized par ticularly by its ruggedness and simplicity of construction, which is effective in operation and which permits of economical manufacture.

A more specific object is to provide in a reversible impact wrench a clutch mechanism which utilizes fiat or abrupt impact surfaces together with a novel and simplified arrangement of parts for automatically and positively positioning the impact surfaces for engagement and for disengaging the same. A related object of the invention is to provide in a power operated wrench, an improved impact clutch especially constructed and arranged whereby engagement and disengagement are positively effected and without dependence upon centrifugal force for operation.

The objects of the invention thus generally set forth together with other objects and ancillary advantages are attained by the construction and arrangement shown by way of illustration in the accompanying drawings in which:

Figure 1 is a central longitudinal section through a power operated wrench embodying the features of the present invention.

Fig. 2 is a fragmentary longitudinal section of the forward portion of the tool shown in Fig. 1 but illustrating the parts in different relative positions.

Figs. 3, 4 and 5 are transverse sections taken respectively in the planes indicated by lines 3 3, 4 4 and 5 5 in Fig. 2. n

Fig. 6 is an exploded perspective view of the impact clutch shown in longitudinal section in Figs. 1 and 2.

Fig. 7 is a fragmentary elevational view taken substantially in the plane indicated by line 7 7 in Fig. 2.

Figs. 8 and 9 are perspective views of the hammer member of the clutch shown in Figs. l, 2 and 6.

While the invention is susceptible of various modifications and alternative constructions, there is shown in the drawings and will herein be described in detail the preferred embodiment thereof, but it is to be understood that it is not hereby intended to limit the invention to the specific form disclosed, but it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings, there shown is an impact wrench or nut runner of the general class used for power driving of nuts, bolts, screws and the like in applying or removing the same. In general, the exemplary impact wrench includes a housing comprising a forward portion 10 and a rear portion 11. The latter is equipped with a pistol-grip handle lzpfarmed,

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integral therewith. Disposed within the rear housing portion 11 is a motor 14 for driving the tool. As shown, the motor is of the reversible, rotary, vane type adapted for actuation by pressure fluid such as compressed air. Thus it includes a cylinder 15 rotatable within which is a rotor 16 equipped with extensible vanes 18. The rotor 16 is fixed on a shaft 19 which is journaled in anti-fric tion bearings 20. The bearings 20 are supportedby end plates 21 which also serve to close the ends of the motor cylinder 15 so as to define a closed rotor chamber.

Pressure fluid to operate :the motor 15 is supplied thereto from any suitable source (not shown) by way of a fitting 22 received in the outer end of a passage generally designated 24 in the handle 12. The admission of pressure fluid to the motor is under the control of a throttle valve assembly indicated generally at 25 and a reversing valve indicated generally at 26. The valves 25 and 26 are respectively equipped with fingerpieces 25a and 26a which are disposed for convenient manipulation by an operator using the tool. From the throttle valve 26, pressure fluid is admitted into the rotor chamber by suitable ports (not shown) in the rear end plate and in the wall of the cylin-1 der 15. Spent pressure fluid is exhausted from the cylin der 15 by way of exhaust ports 27 in the cylinder 15 andi an exhaust slot 2S in the housing portion 11.

Within the forward housing portion 10 is enclosed an impact clutch generally designated 3@ and embodying the present invention. The clutch 3f) serves in the il lustrative tool to couple the motor 14 to a 'spindle-321 which is suitably formed atv its outer end to receive ani adaptor which may be a suitable socket wrench head or the like for engagement with a nut or other fastening: element which is to be applied or removed. The spindle 32 is journaled in a suitable anti-friction bearing 34 in the forward end of the housing portion itl which bearing in the present instance is of annular or sleeve form.

In general, the operation of the clutch 30 is such that so long as torsional resistance to rotation of the spindle 32 does not exceed a predetermined maximum, the spindle will revolve in unison with the drive motor shaft 19. When this predetermined torque resistance is` reached, however, an intermittent disengagement and reengagement of the clutch takes place with a sharp ham-V mer blow being delivered to the spindle 32 upon each such re-engagement of the clutch so that the nut or other member being turned is hammered to effect its rotation. The clutch is reversible in operation whereby the same action obtains for either direction or rotation of the motor shaft 19. Accordingly, the power wrench shown can be used for either running and finally setting or initially loosening and removing a threaded fastening element.

The illustrative impact clutch includes an anvil 35 rigid with the spindle 32, a driver 36 coupled to the motor shaft 19 to transmit rotative force therefrom to a carrier 38'. The carrier is of generally cylindrical form and mounts a hammer member or block 39 and means including an actuator 41 for positively positioning the hammer 39 for engagement with the anvil 35. The carrier 38 is maintained in coaxial relation with respect to the spindle 32 by means of a stub shaft 40 which is received in coaxially disposed recesses 32a and 38a formed respectively in the spindle and carrier.

The hammer 39, as shown, is of generally trapezoidal crosssection and is longitudinally reciprocable in a complementally formed guideway 42 in the carrier 38. At its forward end, the hammer 39 is cut away to define a' forwardly projecting hammer dog 44 'having radially dis-4 posed impact surfaces 45. Similarly the anvil 35, which is rigid with the spindle 32, is provided with a rearwardly projecting dog 46. The anvil dog 46 has complemental radially disposed impact surfaces 48 for` engagement by the impact surfaces 45 of the dog 44 of the hammer 39.

As hereinbefore noted, the clutch 30 includes means for positively positioning the hammer 39 to deliver a blow to the anvil 35 and thereafter to withdraw the hammer so as to permit further rotation of the carrier 38and subsequently to reposition or extend the hammer for the delivery of a succeedingblow to the anvil. This operation is accomplished by the provisionof means for pushing the hammer into anvil-engaging position and, after a blow is delivered, for pulling the hammer clear of the anvil without depending upon cam action between the impacting surfaces for disengaging movement or upon centrifugal force to effect positioning of the hammer with respect to the anvil for engagement of their impacting surfaces.

In the preferred embodiment positioning of the hammer '39 is advantageouslyeffected by a lever actuator 41 of `bell-crank form and is thus generally L-shaped. The

actuator41 includes an arm 51 extending longitudinally of the clutch and an arm 52 extending transaxially of the clutch. The actuator 41 is mounted for limited pivotal movement on an axis perpendicular to the longitudinal axis of the tool. For this purpose in the illustrative device the arm 52 is undercut as at 54 to provide a relatively sharp edge 55 which is fulcrumed on the carrier 3S in the bottom of a transaxially-disposed, L-shaped recess S6 formed by suitably relieving the carrier 38.

To effect longitudinal movement of the hammer 39, an articulated connection is provided between the free end of the arm 52 and the rear end of the hammer block 39. For this purpose in the illustrative tool the hammer block is transversely channeled as at 58 to receive for limited relative movement therein the free end of the arm 52. It will be apparent therefore, upon rocking the actuator 41 on its axis 55, 56 into the position shown in Fig. l, the free end of the actuator arm 52 moves rearwardly, and by virtue of engagement thereof in the slot 58 of the hammer block 39, the latter is moved rearwardly'so as to withdraw the hammer dog 44 into a position wherein it clears the anvil dog 56. Conversely, upon rocking of the actuator 41 so that the free end of the arm 52 occupies the position shown in Fig. 2, the hammer is correspondingly moved forwardly so that the hammer dog 44 is projected beyond the forward end of the carrier 38and into position for engagement of its impact surfaces 45 with complemental impact surfaces 48 of the anvil dog 46.

The actuator 41 is utilized to impart rotative force from the driver 36 to the carrier 38, in addition to its function of shifting the hammer 39 into and out of anvil engaging position. For this purpose a driving connection is provided between the driver and the actuator. Thus, in the present instance, the driver 36 is formed with a cross-arm so as to provide a pair of radially disposed shoulders 36a. The shoulders 36a are adapted to engage complementally formed shoulders 41a on the actuator 41. The shoulders 41a are formed by suitably relieving the top surface of the actuator 41 and have faces that are radially disposed when the actuator is in the position shown in Fig. 2. It will be apparent upon reference to the drawings that rotative force from the motor shaft 19 is imported to the driver 36 through a non-circular connection therebetween and thence to the actuator 41 by engagement of the surfaces 36a and 41a. Movement of the hammer actuator 4l with respect to the carrier 38 is constrained to limited pivotal movement about the axis 55, 56, and for this purpose the carrier 38 is provided with intersecting longitudinal `and transverse, parallel-sided, channels 60 and -61, Arespectively. It will be seen, therefore, that the rotative force imparted to the actuator 41 is transmitted to the carrier 38 by engagement of the sides of the actuator with the sidesfofthefcarrier channels 6ft-'and 61.

To effect movement of the actuator 41 so as to move the hammer 39 forwardly so that the hammer dog 44 is in position to engage the anvil dog 46, the free end arm 51 of the actuator is provided with a cam surface 62 for coaction with the anvil dog 46, whereby to move the actuator arm 51 rearwardly and thus rock the actuator 41 in a counterclockwise direction as shown in Fig. 1. This movement of the actuator 41 results in a corresponding movement of the free end of the actuator arm 52 to the end that the hammer 39 is projected forwardly with respect to the carrier 38. Thus, the hammer dog 44 is projected so that the impact surfaces are disposed for engagement with the impact surfaces 48 of the anvil dog 46. Upon reference to Fig. 7 it will be noted that the cam surface 62 of the free end of the actuator arm 51 tapers gradually from the center line of the arm toward its outer edges, thus providing the aforementioned rocking motion of the actuator 41 in either direction of rotation of the clutch 30.

To insure maintenance of the hammer dog in its forwardly projected position, the anvil dog 46 is formed to occupy a substantial segment of the anvil 35 and is provided with a fiat rear surface 64 for the dwell thereon of the apex of the cam surface 62. As the carrier 38 and actuator 41 are rotated the cam surface 62 traverses one of the shoulders of the anvil dog 46 defined by the intersection of the anvil surfaces 48 an 64, rocking movement of the actuator 41 obtains to project the hammer 39 forwardly, and once the forwardmost position of the hammer is attained, the hammer is positively maintained in such position, as rotation of the carrier 38 with respect to the anvil 35 continues, by the engagement of the apex of the cam surface 62 with the dwell surface 64 of the anvil dog 46. With the hammer thus positively maintained in its forward position, the hammer dog 44 is in position to deliver a blow to the anvil 46.

Upon engagement of the impact surfaces 45 and 48 of the hammer dog 44 and anvil dog 46 respectively, so that a blow is delivered to the anvil 35, rotation of the hammer, the carrier 38 and associated parts stops and a slight rebound or bounce obtains. It will be noted that because of the radial disposition of the impact surfaces 4S and 48 there is no camming action effected therebetween so that a full hammer blow is delivered. Even though at the moment of impact there is a momentary interruption of rotation and a slight reverse rotation of the hammer, its carrier and the hammer actuator, rotative force is still being applied to the hammer actuator 41, the carrier 38, and the hammer 39 by virtue of the coupling thereof with the motor shaft 19 through the driver 36. As hereinbefore noted, this rotative force is applied to the aforementioned parts by engagement of the driver cross head surfaces 36a with the rearwardly projecting shoulder 41a on the-rear surface of the hammer actuator 41. Upon reference to Figs. l and 2, it will be noted that engagement between the driver and the actuator is effected in rearwardly spaced relation to the pivotal axis 55, 56 of the hammer actuator. Thus a force couple about this pivotal axis is established. When the hammer is in a position wherein its dog 44 can engage the anvil dog 46, the cam surface 62 on the free end of the hammer actuator arm 51 is Yout of engagement with the anvil by virtue of its diametrically opposite disposition. Thus the force couple established about the pivotal axis is effective to rock the hammer actuator 41 about the axis 55, 56 in a clockwise direction as viewed in'Fig. 1. Such movement effects a rearward movement of the free end .of the actuator arm 52, and by virtue of its engagement at 58 with the hammer 39 -the latter is withdrawn carrying with it the hammer dog 44 to a position wherein the hammer dog 44 is clear of the anvil dog 46. Since the hammer 39 is positively withdrawn into anvil clearing position, and such movement is vnot dependent on any cammingfaction between the faces -45 and .48 it will be.

appreciated that wear of these surfaces is minimized.- Continued application of rotative force from the motor results, therefore, in rotation of the hammer actuator, carrier, and hammer which rotation accelerates until the succeeding hammer blow is delivered. It will be appreciated that during such rotation the cam surface 62 of the hammer actuator arm 51 will again engage the anvil dog 46 and upon so doing, the hammer actuator 41 is rocked so as to reposition the hammer 39 so that its dog 44 is again disposed in impacting relation to the dog 46 of the anvil 35.

I claim as my invention:

1. In an impact wrench having a rotary anvil unit, a driving spindle, and a rotary hammer unit interposed between thespindle and anvil unit and including a body, a hammer element mounted in said body for movement into and out of driving relation to the anvil unit and disposed in radially offset relation to the axis thereof, a member pivoted between its ends on said body on an axis extending transversely thereof and having at one end an operative connection with the hammer element and having at its other end cam means for coaction with said anvil unit, said connection being operative when the hammer and anvil units are in driving relation to rock said member in a direction to exert a longitudinal pulling force on the hammer element to shift it out of driving relation to the anvil unit, and said cam means being operative in the relative rotational movement of the hammer unit upon release from the anvil unit to move said member in a direction to shift the hammer element positively into driving relation to the anvil unit.

2. An impact wrench comprising, in combination, a driving spindle, a rotatable anvil unit with a radially offset impact surface, a rotatable hammer unit coaxial wi said anvil unit and including a hammer element with a radially offset striking surface engageable with the impact surface of the anvil unit, said hammer unit including a body supporting said hammer element for longitudinal movement parallel to the axis of the body, means including a member pivoted upon said body and interposed between said hammer unit and said anvil unit and providing a driving connection between said'spindle and said hammer unit and being operative to shift said element following an impact of the two surfaces in a direction to disengage them, and said member having a cam surface engageable with said anvil unit upon rotation of the hammer unit relative to the anvil unit to restore said surfaces into impacting relation.

3. An impact wrench comprising, in combination, a driving spindle, a rotatable anvil unit with a radially offset impact surface, a rotatable hammer unit coaxial with said anvil unit and including a body having a hammer element with a radially offset striking surface engageable with the impact surface of the anvil unit, said hammer unit including an actuator for moving the hammer element, and a body supporting said actuator, said hammer element being movable by said actuator in a direction substantially parallel with the axis of the body, means providing a driving connection between said spindle and said hammer unit and operative to shift said actuator in one direction following an impact of the two surfaces whereby to disengage the latter and to release the hammer unit for rotation relative to the anvil unit, and cam means operative in such rotation of the hammer unit relative to the anvil unit to move the actuator in the opposite direction so as to restore said surface into impacting relation.

4. In a power operated tool having a motor and a spindle, an impact clutch for coupling the motor and the spindle comprising, in combination, an anvil rigid with the spindle, a hammer alternately shiftable between a retracted position and a projected anvil-engaging position, a carrier coaxially disposed with respect to said anvil and spindle and mounting said hammer for movement vrotative force thereto and to said carrier, engagement between said driver and actuator being at a point spaced longitudinally from the pivotal axis of the actuator so as to effect pivotal movement of said actuator to retract said hammer when said cam surface is out of engagement with said anvil. v

5. In a power operated tool having a motor and a spindle, an impact clutch for coupling the motor and the spindle, said clutch comprising, in combination, an anvil vrigid with the spindle, aI carrier supporting a hammer alternately shiftable between engaging and non-engaging positions with -respect to said anvil, and'means for effecting movement ofY said hammer between its alternative positions, said means including a rockable member supported on said carrier and having an operative connection with the motor and with said hammer to effect hammer movement into one of its alternative positions, and said member also being operatively associated with said anvil to positively effect movement of said hammer member into the other of its alternative positions during rotation thereof.

6. In a power operated tool having a motor and a spindle, an impact clutch for coupling the motor and the spindle, said clutch comprising, in combination, an anvil rigid with the spindle and having a radially offset and radially disposed impact surface, a hammer alternately shiftable between a retracted position and an anvil-engaging position and having an impact surface correspondingly disposed for engagement with the impact surface of said anvil, a carrier coaxially disposed with respect to said anvil and spindle and mounting said hammer for longitudinal movement parallel to the axis of the tool between the alternative positions thereof, a hammer actuator mounted on said carrier and constrained to limited pivotal movement about an axis transverse to the rotational axis of the carrier, said actuator having a generally transaxially disposed arm operatively connected with said hammer for effecting movement thereof between its alternative positions upon pivotal movement of said actuator and having a longitudinally disposed arm providing a cam surface engageable with said anvil upon rotation of said carrier and an actuator to effect pivotal movement of said actuator for projecting said hammer into anvil-engaging position, and a driver operatively connected with the motor and with said actuator in longitudinally spaced relation to the pivotal axis of the latter to impart rotative force thereto and to said carrier and to effect pivotal movement of said actuator to retract said hammer when said cam surface is out of engagement with said anvil upon further rotation of said carrier.

7. In an impact wrench having a rotary anvil unit providing an anvil dog having a radially disposed impact surface and an elongated, transaxially disposed dwell surface, a driving spindle, and a rotary hammer unit interposed between the spindle and anvil unit and including a body, a hammer element mounted in said body for movement into and out of driving relation to the anvil unit and disposed in radially offset relation to the axis thereof, said hammer unit providing a radially disposed striking surface for engagement with the impact surface of the anvil dog, a member pivoted between its ends on said body on an axis extending transversely thereof and having at one end an operative connection with the hammer element and having a cam at its other end for coaction with said anvil dog, said connection being oper'- i with the dwell surface of said anvil dog to positivelyY maintain the hammer element in such relation substantially until engagement of the striking surface thereof with the impact surface of said anvil dog.

8. In a power operated impact tool having a motor, a spindle, and an impact clutch for coupling the motor and spindle including an anvil rigid with the spindle and a hammer unit interposed between the motor and anvil for deliveringv a hammer blow to the anvil, said hammer unit comprising, in combination, ya hammer element engageable with the anvil, a carrier mounting said hammer element for movement withY respect thereto and into and out of anvil-engaging position, a leverfulcrumed on said carrier and operatively connected with said hammer element for Aeffecting movement thereof, and a driver intero-f posed between said motor and saidrlever providing a driving connection therebetween, said` carrier andk lever having interengaging` portions defininga pivotal for said levertransverse to the rotational axis off the tool and constraining! said lever to limited 'movement about such pivotal' axiswith respect to said carrier, said driver and lever having transaXially-disposed interengaging portions spaced longitudinally from saidY pivotal axis for.

rocking said lever with respect to said carrier so as to effect movement of said hammer element and for imparting rotative force from the motorxto said carrier by way o said lever, and cam means associated Vwith said lever to positively restoreV the lever andthe operativelyV connected hammer element to their or111er],'5ositions` following said rockingl movement.;

i References Cited in the file of this' patent UNITED STATES PATENTS' Y 2,520,920 Fosnot sept. 5, 195o 2,563,711 Fitch Aug. 7, 1951 2,684,738v

VKaplan t July 2,71954 

